1. Field of the Invention
The present invention relates to improved binding materials for foodstuff items to be cooked, and especially to elastomeric silicone binding threads for cookable meats and poultry.
2. Description of the Prior Art
Certain foodstuff products, notably meat items such as roasts and poultry, where appropriate boned, have to be tied before cooking, to maintain their shapes, with thread or string binding which is arranged manually or by machine. In the latter case, the thread is frequently knitted beforehand in the form of a net.
The string which forms the net has to possess a number of properties to be suitable for use in automated machinery:
(i) it must be sufficiently elastic, at room temperature and when hot, as to snugly fit the wide variety of different sizes of the items or articles to be packaged, and maintain shape integrity by compression, when both cold and hot, of the different pieces of meat constituting these articles, especially in the case of boned poultry;
(ii) it must possess, when both cold and hot, physical properties sufficient to withstand the strains and rigors to which it is subjected during knitting of the net, during passage through the automatic packaging machine and also during cooking, and such a thread must possess, in particular, adequate tear strength, shear strength, breaking strength and resistance to elongation;
(iii) it must satisfy legal standards relating to materials in contact with foodstuffs;
(iv) it must be insensitive, when both cold and hot, to UV radiation, oxygen, ozone, microwaves and animal and vegetable fats;
(v) it must be, where appropriate, transparent and colorless, and remain so after cooking for reasons of attractive appearance and presentation;
(vi) it must, above all, possess good heat resistance, at least up to 250.degree. C., the maximum temperature of most ovens for cooking food, and possess a satisfactory appearance after cooking and not stick to the meat. In addition, in cases where the thread has been overheated, it is necessary that the degradation products of the thread be nontoxic when ingested into the human body.
Threads or strings for meat items to be roasted have long been proposed to this art. For example, strings made from plant fibers have thus been used, which possess the major drawback of being inelastic and, consequently, of cutting into the meat and, in particular, of being unsuited for use in the form of threads and nets in automatic packaging machines.
Such string is being replaced in industrial installations by a hydrocarbon-based natural or synthetic rubber latex thread.
However, this type of thread is degraded when heated to temperatures of 70.degree. C. and above, and loses its elasticity and mechanical characteristics, and the fumes originating from its degradation are strong irritants to the throat and the respiratory tract and can possess some degree of toxicity. Moreover, since these threads do not have textile appearance and handle, and the nets made therefrom also do not have cohesion and sufficient resistance to elongation, it has been proposed to cover these threads in a polyamide sheath.
This covering admittedly provides the requisite cohesion and resistance to elongation, but it is a very expensive operation and, in addition, the polyamide thread has a very unsatisfactory appearance after cooking, sticks to the meat and is degraded to chemicals which may be toxic.
Hence, serious need exists in this art for a binding material, especially a string, thread or fiber, for packaging foodstuff products to be cooked, which does not possess the disadvantages and drawbacks of the known fibrous materials useful for such purpose, while at the same time exhibiting the combination of physiochemical properties listed hereinabove.